This plugin is useful if you use plugins which define lots of maps and it is not easy remember them at first (for example some latex plugins). It provides commands:
Map[!] {pattern}
Nmap[!] {pattern}
Imap[!] {pattern}
Smap[!] {pattern}
Vmap[!] {pattern}
Omap[!] {pattern}
Lmap[!] {pattern}
They will list maps which rhs matches the vim {pattern}. If bang is used the {pattern} is matched by the output of the corresponding map command with only first column removed (which indicates the mode).